Control knobs are commonly used on a variety of commercial and residential appliances to control an operating condition of the appliance. Control knobs are particularly common on cooking appliances, such as stoves or cooktops. Various shapes and sizes can be used depending upon, e.g., the intended application, aesthetics, and other factors.
For example, cooktops traditionally have at least one heating element positioned at a cooktop surface for use in heating or cooking an object, such as a cooking utensil, and its contents. The at least one heating element may heat a cooking utensil directly through induction heating, or may use another heat source such as electrically resistant coils or gas burners. Control knobs are typically used to adjust the power level of the heating element—and thus the amount of heat delivered by the heating element. In other appliances, e.g., ovens, washing machines, clothes dryers, etc., control knobs are often used to select an operating mode of the appliance, such as “bake” or “broil” for ovens, “cotton” or “permanent press” for clothes dryers, etc. Often the position of the control knob, and thus the operating mode or power level setting it controls, is not readily visible to a user of the appliance from a distance, for example, across the kitchen from the dining room.
To provide a user with easily visible feedback regarding the setting of the power control and thus the power being supplied to the heating element, cooktops with electronic controls, e.g., touch-sensitive controls, generally include a display for communicating to the user a status of the heating element. For example, displays may typically include a plurality of LED indicators that are mounted on a control panel and illuminated to indicate the setting of the power control of the appliance. Often this display is in to form of “7-segment” numerals, indicating the power level as “L”, “0”, “1”, . . . “9” to “H”; it is often difficult for a consumer, especially one with visual impairment, to distinguish these digits from a distance or from an off-axis viewing angle. Worse yet are cooktops with control knobs, which, generally, only provide a painted or engraved “pointer” line along the edge of the knob, which requires the operator to be in close proximity to the cooktop to determine the position of this “pointer” relative to the markings printed on the control panel below. These are extremely difficult to see from a distance, especially if the “pointer” marking is on the side of the knob opposite the operator of the cooktop. For this reason, it would be advantageous to provide an electronically illuminated indication of the knob's angular position, which could be seen from a farther distance (and over a wider range of viewing angles) than the current implementation.
Determining the angular position of the control knob typically requires measuring the rotation of a stem extending from the control knob, or the rotation of a control shaft (e.g., from a gas flow valve within the appliance) which extends upwards into the stem of the knob. Typically, appliances use a rotary position sensor positioned underneath the control panel that directly connects to and/or extends from the control knob stem. However, methods of illuminating the control knob or surrounding areas typically require the placement of a light source and/or light guide directly underneath the control panel near the control knob. Complicated lighting systems or rotary position sensor arrangements may be required to fit both of these components in the minimal space available within the appliance underneath the control panel. In the case of a gas cooktop, the control shaft is part of the gas valve assembly, and the shaft encoder must be something which can be added-to the system without disturbing the existing system, i.e., the shaft must extend through the encoder.
Certain types of appliances, such as gas cooktops, often require the ingestion of air into the appliances for the purposes of gas burner combustion. Often an electric appliance requires the ingestion of air for the cooling of electrical components within the chassis of the appliance. In such appliances the only practical inlet of said air is through a gap between the knob stem (or gas valve shaft) and the opening in the control panel. The inclusion of traditional optical shaft encoders and optical components for illuminating the graphics around the control knob are generally not conducive to adequate airflow for the appliance.
Accordingly, a consumer appliance having a control knob with an improved knob illumination assembly is desirable. More particularly, a control knob assembly that can accurately illuminate a portion of the consumer appliance to provide an easily visible indication of the angular position of the control knob and status of the heating element (or other functionality) while minimizing the amount of space required underneath a control panel of the consumer appliance would be particularly beneficial. Additionally, it would be particularly beneficial if the control knob angular position sensing and graphical illumination subsystem was arranged in such a way that little hindrance of airflow was encountered.